From 3fb66056d6b9d95e4332be38d55e52e83190400f Mon Sep 17 00:00:00 2001
From: Albrecht Schlosser <albrechts.fltk@online.de>
Date: Fri, 25 Mar 2022 15:02:53 +0100
Subject: CMake: add missing variable initialization

Although CMake uses previously undefined variables like empty strings
it could happen that variables set in the calling context by other
projects initialized some variables with unexpected values.

Example: FLTK_LIBRARIES could have been initialized by previous
  execution of 'find_package(FLTK ...)' in a project using FLTK
---
 CMake/setup.cmake | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

(limited to 'CMake/setup.cmake')

diff --git a/CMake/setup.cmake b/CMake/setup.cmake
index 8ac22fbbb..434697993 100644
--- a/CMake/setup.cmake
+++ b/CMake/setup.cmake
@@ -37,7 +37,6 @@ set (FLTK_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 
 include(GNUInstallDirs)
 
-
 set (FLTK_BINDIR ${CMAKE_INSTALL_BINDIR} CACHE PATH
   "Binary install path relative to CMAKE_INSTALL_PREFIX unless set to an absolute path.")
 set (FLTK_LIBDIR ${CMAKE_INSTALL_LIBDIR} CACHE PATH
@@ -52,6 +51,20 @@ set (FLTK_DOCDIR ${CMAKE_INSTALL_DATADIR}/doc CACHE PATH
   "Non-arch doc install path relative to CMAKE_INSTALL_PREFIX unless set to an absolute path.")
 
 
+#######################################################################
+# initialize internally used variables
+# some of these variables are used to *append* other values later
+#######################################################################
+
+set (FLTK_LDLIBS "")
+set (FLTK_LIBRARIES "")
+set (GLLIBS "")
+set (IMAGELIBS "")
+set (LDFLAGS "")
+set (LIBS "")
+set (LINK_LIBS "")
+set (STATICIMAGELIBS "")
+
 #######################################################################
 # platform dependent information
 #######################################################################
-- 
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